Dry Mouth (Xerostomia): Causes and Management
Primary Causes
Medications are the most common cause of xerostomia in both the general population and older adults, primarily through anticholinergic side effects, with polypharmacy significantly increasing risk. 1, 2
Medication-Induced Xerostomia (Most Common)
The following drug classes cause dry mouth through various mechanisms:
- Anticholinergic medications: Tricyclic antidepressants, antihistamines, antimuscarinics, antiparkinsonians, and antipsychotics directly block salivary gland stimulation 3, 1
- Cardiovascular drugs: Beta-blockers (atenolol > propranolol), calcium channel blockers, and centrally acting antihypertensives like clonidine 1
- Psychiatric medications: SSRIs (especially fluoxetine at higher doses), bupropion, and anxiolytics 1
- Pain medications: Opioids commonly cause xerostomia 1
- Stimulants and weight loss drugs: Phentermine, lisdexamfetamine, phentermine/topiramate, and naltrexone/bupropion 1
- Other medications: Diuretics, lithium, NSAIDs (prolonged use), decongestants, and analgesics 3, 1
Autoimmune and Systemic Diseases
- Sjögren's syndrome: The primary autoimmune cause, affecting 0.4% of the population with a 20:1 female-to-male ratio, characterized by lymphocytic infiltration of salivary and lacrimal glands 1
- Other autoimmune conditions: Rheumatoid arthritis, systemic lupus erythematosus, scleroderma, and primary biliary cholangitis 1
- Metabolic diseases: Diabetes mellitus, heart failure, chronic kidney disease, and metabolic syndrome 1
Radiation-Induced Xerostomia
Radiation therapy to the head and neck causes salivary gland dysfunction that dramatically increases the risk of dental caries, dentoalveolar infection, and osteoradionecrosis. 3
- IMRT (intensity-modulated radiation therapy) significantly reduces xerostomia compared to conventional radiotherapy: 38% vs 74% experienced grade 2 or worse xerostomia at 1 year 3
- Radiation-related caries can appear within the first 3 months following treatment 3
Age-Related and Other Factors
- Aging: Salivary flow rate declines with age, making older adults more susceptible even without other risk factors 1
- Dehydration: Fluid intake restrictions and dehydration from any cause worsen xerostomia 1
- Neurological conditions: Parkinson's disease, stroke, dementia, and autonomic dysfunction 1
Clinical Evaluation
Key Diagnostic Steps
Medication review: Identify all medications with anticholinergic or anti-adrenergic effects; consider dose reduction or alternatives 3, 2
Assess for autoimmune disease: Screen for Sjögren's syndrome symptoms (dry eyes, joint pain), check for reduced salivation and scleroderma on examination 3, 1
Measure salivary flow objectively: Patient's subjective sensation may not correlate with actual output; measure whole salivary flow rates before initiating treatment 1
Rule out mimicking conditions: Candidiasis, burning mouth syndrome, and dysphagia can present similarly 1
Blood tests: Electrolytes/renal function, thyroid function, calcium, HbA1c to identify systemic causes 3
Management Strategies
Non-Pharmacological Interventions (First-Line)
Comprehensive management should emphasize patient education, lifestyle modifications, and palliative measures before considering pharmacological treatment. 4
- Saliva substitutes: Products containing xylitol (such as Biotene) provide symptomatic relief 5, 2
- Sugar-free chewing gum: Stimulates residual salivary function 4
- Frequent water sips: Maintain oral moisture throughout the day 4
- Excellent oral hygiene: Critical to prevent dental complications 3
- Topical fluoride interventions: Essential for caries prevention in chronic xerostomia 4
Pharmacological Treatment
Pilocarpine hydrochloride is FDA-approved for treating dry mouth from radiation-induced salivary gland hypofunction and Sjögren's syndrome. 6
Pilocarpine Dosing:
- Radiation-induced xerostomia: Start 5 mg three times daily; may increase to 10 mg three times daily if tolerated 6
- Sjögren's syndrome: 5 mg four times daily (20 mg/day) showed statistically significant global improvement compared to placebo at 6 weeks 6
- Common side effects: Sweating (most common cause of withdrawal at 12% with 10 mg TID), nausea, rhinitis, diarrhea, chills, flushing, urinary frequency 6
Alternative: Cevimeline or malic acid may attenuate symptoms 7
Special Considerations for Radiation Therapy Patients
Pre-radiation dental evaluation must be completed at least 2 weeks before starting radiotherapy, with extractions performed if indicated based on long-term tooth prognosis. 3
Post-treatment goals include:
- Managing xerostomia aggressively 3
- Preventing and treating dental caries 3
- Preventing post-radiation osteonecrosis 3
- Preventing and managing oral candidiasis 3
- Dental recall visits at least every 6 months, more frequently for those with active xerostomia or new caries 3
Critical Pitfalls to Avoid
- Do not rely solely on patient's subjective complaint: Measure salivary flow objectively, as perception may not match actual output 1
- Do not overlook polypharmacy: Elderly patients face substantially higher risk due to multiple medications combined with age-related decline 1
- Do not ignore systemic causes: Screen for diabetes, heart failure, renal failure, and autoimmune diseases 1
- Do not delay dental intervention in radiation patients: Extractions after radiation carry high risk of osteoradionecrosis; complete dental work before treatment 3
- Recognize paradoxical effects: Acetylcholinesterase inhibitors for Alzheimer's disease actually increase saliva production, contrasting with most medications 1
Complications of Untreated Xerostomia
Chronic xerostomia significantly increases risk of dental caries, demineralization, tooth sensitivity, candidiasis, and other oral diseases that negatively affect quality of life. 4